The present invention relates to an exhaust gas filter and especially to an exhaust gas filter for removing solid ingredients such as worn-away powder contaminated by radioactivity.
In nuclear facilities such as nuclear power plants and accelerators, waste oil is produced during operation if an oil-supply rotary vacuum pump is used to obtain vacuum. So oilless dry vacuum pumps are widely used.
However, even in a dry vacuum pump, grease for lubricating a rotary portion is likely to deteriorate by radioactivity. JP11-210658A proposed a vacuum exhaust device that comprises a solid lubricating bearing for a rotary part.
But, even if the solid lubricating bearing is used, a vacuum pump will have air-tight tip seals at the end of the rotary part. With operation, the tip seals are worn away and released in air.
To prevent it, a filter is provided in an exhaust tube or other tubes to filtrate a gas and to catch fine powder contained in an exhaust gas.
However, workers are likely to be exposed to radioactivity in the exhaust gas when the filter is repaired or replaced. It is required to provide effective means for removing fine powder contaminated by radioactivity in the exhaust gas discharged from the dry vacuum pump.